1. Technical Field
This invention relates to a wiring board, a semiconductor device and a semiconductor element, and more particularly to a wiring board on which a semiconductor element with electrode terminals on the entire face of the one side thereof is loaded, a semiconductor device with the semiconductor element loaded on the wiring board, and a semiconductor element loaded on the wiring board.
2. Related Art
On the one side of a wiring board 100 with a conventional semiconductor element 102 loaded thereon as shown in FIG. 12A, formed is a semiconductor element loading face having a wider area than that of the semiconductor element 102 to be loaded. On the semiconductor element loading face, pads 104, 104, . . . are formed which are to be connected with electrode terminals formed in the vicinity of the edge of the semiconductor element 102.
From these pads 104, 104, . . . , wiring patterns 108 are drawn out to via pads 106 formed in the vicinity of the edge of the semiconductor element loading face outside the semiconductor element 102 to be loaded, respectively.
In contrast to such a semiconductor element loading face, on the backside of the wiring board 100, as shown in FIG. 12B, external connecting pads 114, 114, . . . are arranged in a lattice pattern. The via pads 106, 106, . . . are connected to pads 110 through vias passing through the wiring board 100 and further connected to the corresponding external connecting pads 114 through wiring patterns 112.
Meanwhile, in recent years, with development of high performance and miniaturization, the electrode terminals of the semiconductor element has been formed with high density. Namely, as shown in FIG. 10, electrode terminals 202, 202, have become formed on the entire face of the one side of the semiconductor element 200.
In the wiring board on which a semiconductor element 200 is to be loaded, as shown in FIG. 10, on the semiconductor element loading face, the loading pads corresponding to the electrode terminals 202, 202, . . . of the semiconductor element 200 must be formed, and the wiring patterns 108 must be also drawn from the loading pads to the via pads 106 formed in the vicinity of the edge of the wiring board, respectively.
However, the pitch between the loading pads corresponding to the electrode terminals 202, 202, of the semiconductor element 200 is so narrow that the number of the wiring patterns capable of being formed between the loading pads is limited. As a result, with the wiring board being formed of multiple layers, the wiring patterns which cannot be formed must be drawn to the via pads 106.
The following Patent Reference 1 discloses a semiconductor device in which the semiconductor element 200 with the electrode terminals 202, 202, . . . formed on the entire surface of the one side is loaded on the board with the wiring board being not formed of multiple layers.
FIG. 11 shows such a semiconductor device. In the semiconductor device shown in FIG. 11, the electrode terminals 202, 202, . . . of the semiconductor element 200 are electrically connected with the corresponding external connecting terminals 206, 206 formed on a board 204 through soldering bumps 208, respectively.
[Patent Reference 1] JP-A-10-284538
In the semiconductor device shown in FIG. 11, without routing the wiring patterns on the board, the electrode terminals 202, 202, . . . of the semiconductor element 200 are electrically connected with the corresponding external connecting terminals 206, respectively.
In the semiconductor device shown in FIG. 11, however, the external connecting terminals 206 of the board 204 are formed immediately below the electrode terminals 202 of the semiconductor element 200 so that the pitch between the electrode terminals 202, 202, . . . of the semiconductor element 200 is equal to that between the external connecting terminals 206, 206, . . . of the board 204. Owing to this fact, the number of the external connecting terminals 206 capable of being formed at the board 204 will be limited.
Further, it is required that the pitch between the external connecting terminals 206, 206, . . . formed on the board 204 is changed in the relationship with the mounting pads of a mounting board in which the semiconductor device is mounted.
However, it is very difficult to satisfy this requirement in the semiconductor device shown in FIG. 11 because the pitch between the electrode terminals 202, 202, of the semiconductor element 200 must be first changed.